Reaper DAW, External Hard Drive, misery

Hi.

I am a musician and I use a Digital Audio Workstation called Reaper. Well-known in the industry.

I had a Lenovo PC and in recording files, required more hard drive space. So i bought a one-T external drive.

Before I made the switch, I moved all my recording projects (.rpp is the extension, and it contains .wav files) to the external hard drive.

Now, plugged into the iMac (the 5 k one) the projects load but cannot "find" the attendant .wav files. I know they're "there" because searching for them yields results, but my DAW just doesn't load them. I click "search for file", and even though I KNOW they're on the portable drive, the project doesn't see them to load them after a search.

Is there anyone out there who's had this issue?

Thanks.